1. Field of the Invention
The invention relates to an article that exhibits its characteristics by receiving or reflecting a light, particularly an inorganic paint composition useful for protecting the surface of a solar panel of a solar generator system and a mirror capable of obtaining a transparent and tenacious coating film.
2. Description of the Related Art
Various inorganic paint compositions using an alkali metal silicate as a binder have been proposed.
However, most of the coating films obtained are fragile, and fine cracks are generated by distortion when the coated subjects are expanded and contracted due to temperature changes to impair weather resistance and pollution resistance of the coating film.
Accordingly, the inventors of the invention have invented an inorganic paint composition prepared by adding a polyvalent metal-containing hardener such as calcium silicate and zinc phosphate to an alkali metal silicate, and by further adding, as an inorganic filler, a fine powder of a natural glass having a borate component-dissolving action mainly comprising colemanite and ulexite (see Japanese Patent Application Publication Nos. 3,140,611 and 3,140,612).
A tenacious coating film could be obtained in these inventions since boric acid is dissolved by mixing with water, and dissolved boric acid and the binder are simultaneously solidified when the mixed solution is dried after coating. These inorganic paint compositions have been widely recognized as coating film-forming agents for protecting the surfaces of commonly used exterior and interior construction materials and interior materials of underground passages.
However, the inorganic paint compositions described above are naturally almost impermeable to light since they contain a natural glass fine powder. Accordingly, they are not suitable as materials exhibiting their characteristics by receiving a light, for example as a solar panel of a solar generator system, and as materials that exhibits their characteristics by reflecting a light, for example as a surface protecting film of a mirror.
On the other hand, since natural minerals such as kaolin, talc and bentonite were added as fillers for improving tenacity of the coating film in inorganic paint compositions proposed by other inventors, light permeability thereof has remained insufficient.